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1. case the heating curve can be lowered with about 10 to 15 C an energy saving of 2 of the total energy consumption for heating is reached due to preventing this overshoot that otherwise not can be influenced by the users In practice higher energy savings are likely because overshoot in general not only the part that can not be influenced will be prevented The sum of these 3 effects add up to a total energy saving of about 5 on the energy consumption for heating assuming a reduction of the heating curve with about 10 to 15 C Our research showed that such reductions are often possible In case of higher or lower reductions the energy saving are of course also higher or lower As additional benefits can be mentioned 1 2 the fact that insight can be obtained in the thermal balance between various apartments Or in other words whether or not similar inside air temperatures occur in various apartments If this is not the case this points to an incorrect heat distribution local not expected extra heat losses etc If the thermal balance is not correct based upon this insight additional actions can be performed to improve the functioning of the heating installation the fact that by lowering the heating curve users will have less need to close the radiator valves This will lead to a better functioning of the central control of the heating system Error Unknown switch argument Demonstration of the method The software prog2. the inside air temperature in the apartments and the outside air temperature In formula T x T Y 6 The parameters X y a b are derived by a least squares method 2 to determine based upon these correlations with PC software the supply water temperature as function of the outside air temperature by which the inside air temperature equals the desired value T The equation with the layout of formula 2 that can be derived upon the measured correlations is p Cine py a DATe Ym bn xm 1 xm 1 The principle of the heating curve adjustment method is graphically illustrated in figure 1 inside temp f outside temp supply temp f outside temp 30 T measured 14 On tp 2 Mie A i ure i meagured i 25 yey 80 i i i i i 1 desired value po SEL A re a a a a a See Owes case ey i eee ci a i i i i nee rales ere reese en 0 1 1 i i I i 0 5 0 5 10 15 20 10 5 0 5 10 15 20 one or more apartments heating plant front view apartment building figure 1 Principle of the heating curve adjustment method Error Unknown switch argument Performance of the method in practice The performance of the method in practice consists of 4 parts namely 1 short term measurements continuously monitoring to determine the correlation between 1 supply water temperature and 2 inside air temperature with the outside air temperature 2 the determination of the
3. The Heating Curve Adjustment Method Clima 2000 paper P343 topic 10 Software W Kornaat and H C Peitsman TNO Building and Construction Research The Netherlands The Heating Curve Adjustment Method by W Kornaat phone 31 15 2608568 fax 31 15 2608432 H C Peitsman phone 31 15 2608518 fax 31 15 2608432 TNO Building and Construction Research The Netherlands Introduction In apartment buildings with a collective heating system usually a weather compensator is used for controlling the heat delivery to the various apartments With this weather compensator the supply water temperature to the apartments is regulated depending on the outside air temperature With decreasing outside air temperature the supply water temperature is increased because of the increase in the heat demand The relation between the supply water temperature and outside air temperature is called the heating curve After implementation these heating curves are usually set according to the design of the heating system Often there is no check whether this setting is indeed correct in practice Due to safety marges in the design in practice often a some what lower heating curve is possible Furthermore in practice adjustments on the heating curves are often used as an easy way to prevent complaints Heating curves are for instance increased in case of complaints about too low inside air temperatures The actual cause for the complaints is often not further inves
4. a correct determination of the heating curve situations with important solar radiation need not be considered for the analysis In steady state conditions an energy balance of a building yields GaN eT Ka Ey ee 1 G is the global heat losses coefficient per cubic meter W m K V is the volume of the heated zone m K is the heat emission coefficient W K T is the mean indoor temperature C T is the outdoor temperature C T is the water flow temperature C A are the free heat gains W This equation can be arranged as follows and gives the general form for a heating curve T a T b 2 where a GV K 3 b G V K K T A K 4 This reasoning shows that an energy balance that takes into account the characteristics of e the building by way of the parameters G and V the installation by way of the parameters T and K the climate by way of the parameters T the thermal comfort by way of parameter T the internal situation by way of parameter A leads to a linear relationship between the water flow temperature T and the outdoor air temperature T Error Unknown switch argument The basic principle of the heating curve adjustment method is 1 to determine by means of measurements the correlation between the supply water temperature to the apartments maintained by the weather compensator and the outside air temperature In formula T a T b 5 and the correlation between
5. boilers are given for various situations amongst which the type of boiler control 5 calculations performed with the model of a Dutch boiler manufacturer Error Unknown switch argument 2 3 a reduction of the transport heat losses From the Dutch ISSO publication 25 6 is derived that the heat loss by transport pipes can be reduced with about 20 in case the heating curve is reduced with 10 to 15 C The actual energy saving now depends per situation on the initial transport heat losses For an average Dutch situation we have determined that based upon 20 reduction of the heat loss by transport pipes about 1 on the total energy consumption for heating can be saved a reduction of the temperature overshoot in the apartments Due to a high heating curve an overshoot of the air temperatures in the apartments is possible leading to unnecessary energy losses This overshoot is however hard to calculate and depends on many things as for instance the control of the radiators the dimensions of the radiators etc A part of this overshoot can however not be influenced by the users This is the part when the heat production caused by the transport pipes in the apartments exceeds the heat demand of the apartment The users can not control this heat production by the transport pipes as they can control the heat production through the radiator by closing the radiator valves For a typical Dutch apartment building is determined that in
6. current settings of the weather compensator 3 the construction of an input file based upon part 1 and 2 suitable for the computer program WINREG by which the optimum heating curve will be determined 4 The analysis and the determination of optimum heating curve with the computer program WINREG A flow chart of the method is given in figure 2 The various parts of the method are in the following further discussed Short term measurements Inventory of weather compensator Parameters to be measured For instance supply water temperature of the weather current setting of heating curve compensator period of night setback inside air temperature s etc outside air temperature Measuring time 3 to 6 weeks depending on variation in outside air temperature Construction of an input file suitable for determination of the optimum heating curve Using the computer program PREPATV or a common spreadsheet program all measured data plus some extra information needs to be put in the correct format Analysis and determination of the optimum heating curve Using the computer program WINREG both these computer programs are developed specific for the heating curve adjustment method figure 2 Flow chart of the heating curve adjustment method Error Unknown switch argument Short term measurements The following parameters need to be measured 1 2 3 the supply water temperature to the apartments
7. d out During the day furthermore only the situations in which the actual heating curve is functioning need to be considered Periods in which the supply water temperature is limited need not be considered see figure 4 The measurements with limited supply water temperature will make the correlation incorrect Construction of the input file As already mentioned the use of several small data loggers is recommended for the measurements After performing the measurements the data of these several loggers need to be put in 1 file for further analysis concerning the optimum heating curve Special attention hereby needs to be given to the time synchronisation For this purpose a special computer program PREPATYV is developed For a description of this computer program is referred to 3 A few features of this computer program however does not function well This can give problems depending upon the used measuring equipment and actual measuring results A more general option is to construct such an input file using a spreadsheet program Often a spreadsheet program is already used to visualize the measured data In this case it is an easy step to arrange the data in the spreadsheet to a format suitable for further optimizing of the heating curve Analysis and determination of the optimum heating curve WINREG The computer program developed for this purpose is called WINREG For a description of this computer program is referred to 4 After read
8. data is actually deleted For the filtering the period of night setback is used while furthermore in WINREG several filter parameters can be set to maintain only data in which the actual heating curve see figure 4 is active Furthermore it is possible to filter out days manual For instance days with high solar radiation Due to the effect on the inside air temperature such situations can disturb a correct analysis Next with the computer program WINREG the correlation between inside air temperature and outside air temperature is determined The measurements V Tin Mes and correlation Tin Corr can be graphically presented see figure 7 the correlation between supply water temperature and outside air temperature is determined The measurements A Tdep Mes and correlation Tdep Corr can be graphically presented see figure 8 based upon the previous correlations the optimum heating curve is determined The optimum heating curve A Tdep New and the current heating curve Tdep Init are also visualized in figure 8 Figure 7 shows that in this particular situation the occurring inside air temperatures are too high The result of the evaluation with the WINREG program is therefor that the heating curve can be set lower as illustrated in figure 8 with 12 to 17 C 7 Tin Mes Inside T E Tin Corr 5 Outside T figure 7 Correlation between inside air temperature and outside air temperature Error Unknown switch a
9. front view of apartment building Current setting weather compensator The current setting of the weather compensator needs to be determined such as 1 the setting of the heating curve 2 limitations on the heating curve e g maximum limitation at low outside air o temperatures see figure 4 3 period with night setback 4 etc 100 maximum limitation 80 60 t s 4 41 1 40 The setting of the heating curve is of course needed to make a comparison with the measured curve and to evaluate whether the weather compensator on this point functions correctly The other information is necessary to filter the 20 40 o 10 measured data This filtering takes place during outside air temperature C gt the actual determination of the optimum heating curve with the computer program WINREG see later on For this determination for instance only the measurements during the day are needed Based upon the period of night setback the supply water temperature itside a 1 1 1 1 1 PE AEE 4 20 actual heating curve I i ou H H H t siaii a Soe PSS J H S I i i i I i 20 30 figure 4 Inventory of heating curve Error Unknown switch argument night period with usually lower heating curve and the heating up period at the start of the day are determined and rule
10. ing the previous mentioned input file this computer program first gives a window with general information see figure 5 such as location of the measurements place name measuring interval sampling rate number of measurements number of samples period with night setback current setting of the heating curve initial controller adjustment etc The measured data can be visualized with the program see figure 6 Error Unknown switch argument SS pitas Se Betti aes 3 it cree Sere p E i Spree EEIE Ee ee File Treatment Results Options File C HEATPROG INS TALL WINREGA NL DEMO DEMO _DAT Last save 27 11 96 12 03 Place name Measurement start time 3 2 95 09 19 Initial controller adjustment Sampling rate min 5 Tout C Tdep C Number of samples 3795 1 Adjustment point Number of inside temperature sd 2 Adjustment point C 15 C 55 Night setback working Yes Night setback start time Night setback end time figure 5 General information concerning the measurements EKlTat CIT dep I Tint 372795 PT g P Sacos P US Er T dep TCO a Tint T out Hours figure 6 Visualization of the measured data in WINREG T dep supply water temp T inl inside air temp T out outside air temp Error Unknown switch argument For the determination of the optimum heating curve the computer program WINREG filters the data remaining only the necessary data It is noted however that no
11. is not the case this can point out an incorrect heat distribution hydraulic unbalance local unexpected extra heat losses or local insufficient radiator capacity These problems need to be tackled in general for creating a good heating system and in special before an optimum heating curve can be determined Because measurements need to be performed on various locations in the building see figure 3 a good option is to use several small one or multichannel data loggers The installation effort per apartment can then be minimized to about half an hour Several different types of such data loggers are nowadays available The measurements need to be performed during a period in which a sufficient variation in the outside air temperature occurs on which a good correlation with supply water and inside air temperatures can be made In practice this comes down to roughly 3 to 6 weeks Error Unknown switch argument heating plant supply water temperature e outside air temperature fale EEAS oa apartments e inside air temperature measured in a maximum of 8 rooms e with radiator valves fully opend e by prefence measure in livingroom or kitchen e selection of apartments close to and far away for heating plant in relation to distribution heat losses with high and low heat demand apartments on top floor apartments in the middle of the buidling etc if possible apartments with complaints figure 3 Overview of measurements in
12. maintained with the weather compensator This temperature can be accurate enough measured using an at the outside well insulated surface sensor attached on the water pipe This temperature needs to be measured as close as possible to the sensor of the weather compensator In this way also the functioning of the weather compensator can be checked the outside air temperature The outside air temperature needs to be measured on a location shielded from solar radiation It may be expected that usually a place besides the sensor of the weather compensator will be correct the inside air temperatures It is advised to measure the inside air temperature in the living rooms because these are commonly the most important and occupied rooms During the measurements the radiator valves need to be fully opened This is done because in this situation the weather compensator needs to be able to maintain the desired inside air temperature The software developed for the heating curve adjustment method can handle a maximum of 8 inside air temperatures measured in different apartments Measuring in more apartments increases the accuracy of the method Furthermore by measuring in apartments spread over the apartment building far and close to the boiler room on the top floor the ground floor or an other floor etc an insig ht is gained in the thermal balance in the building This means occur in different apartments similar inside air temperatures If this
13. often set much too high Lowering the heating curves with a least 10 to 15 C was possible in almost all the considered apartment buildings It is predicted that the use of the heating curve adjustment method in such cases can lead to an energy saving for heating of about 5 Error Unknown switch argument Literature 1 The heating curve adjustment system S Nibel CSTB Paris France September 1994 2 Transfer of a heating curve adjustment method and implementation with BEMS Final report EC Sprint program Contract RA 159 ter March 1996 3 PREPATV User manual Presentation and use of the software March 1996 4 WINREG User manual Presentation and use of the software March 1996 5 ISSO publication 20 Stichting ISSO Rotterdam 6 ISSO publication 25 Stichting ISSO Rotterdam Error Unknown switch argument
14. rams will be demonstrated during the Clima 2000 congress Resume The heating curve adjustment method provides an easy way to fit the heating curve for a building leading to an improvement of the thermal comfort within the building and or reduction of the energy consumption Due to the combination of measurements over a longer period and analysis with computer software a rational adjustment can be determined and made This is a large improvement in relation with manual adjustments that are mostly used up to now based upon occasional findings and or measurements It is indicated as an easy way because in total it will cost about 2 or 3 days per building to perform the method This means installing the measuring equipment collecting and analyzing the data determining the optimum heating curve removing the measuring equipment Furthermore there are little or no restrictions on the measuring equipment to be used This means that users can use their own equipment with which they are familiar Due to the set up of the method and the guidelines the method can also be used by people who are less familiar with the technical aspects of heating plants The method can therefor not only be used by heating engineers and installers but also for instance by building owners municipal energy managers etc This enlarges the possible use of the method in practice During our research in the Netherlands it was our finding that the heating curves were
15. rgument PA E EE EEE ae a EE RSG BE MT AINE DNE THS fue ey Tabet R is ce ero re ESTEE A Tdep Mes E Tdep nt Tdep Cort Tdep New figure 8 Correlation between supply water temperature and outside air temperature plus the current and optimum heating curve setting Benefits of the method results The primary benefit of the method is to obtain a setting of the weather compensator suited for the specific building This will contribute to a good thermal comfort in the building This means in cases were the heating curve was set too low adjustments are determined to prevent too low inside temperatures and in cases were the heating curve was set too high adjustments are determined to prevent too high inside temperatures It is our finding that the heating curves in practice are mostly set too high because adjustments on the heating curves are often used as an easy way to prevent complaints about to loo inside temperatures In these cases optimizing the setting of the heating curve will also result in a reduction of the energy consumption Energy savings due to optimizing lowering of the heating curve is realised by the following issues 1 a reduction of the boiler heat losses improvement of the performance coefficient of the boiler This energy saving is determined to be about 2 of the total energy consumption for heating This is based upon the Dutch ISSO publication 20 in which the performance coefficients for
16. tigated and the heating curve is often not set back and kept at an unnecessary high level in the future The result of the above mentioned is that in a lot of situations the setting of the heating curve will not be the optimum for the specific building This can amongst other things lead to thermal discomfort and unnecessary energy consumption A method for determining the optimum setting of the heating curve in practice is developed by CSTB France 1 With this method an easy and rational optimalisation can be obtained Within the framework of the Sprint program of the European Community this method is tested and improved by cooperation between CSTB France CSTC Belgium IBP Germany SINTEF Norway and TNO the Netherlands 2 In this article the principle of this method the performance of this method in practice and the benefits of using the method are described Error Unknown switch argument Principle of the method The method for adjusting the parameters of the heating curve is based on a simplified representation of the system building central heating plant control unit This means that steady state conditions are assumed a linear heat emission of the heat emitters is assumed no other terminal control devices besides the heating curve are considered or may be active e g all radiator valves need to be fully opened the effect of solar radiation is not taken into account This means that for
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